// Copyright (c) 2026, Pim van Pelt <pim@ipng.ch>

package health

import (
	"testing"

	"git.ipng.ch/ipng/vpp-maglev/internal/config"
)

// TestBackendEffectiveWeight locks down the state → (weight, flush) truth
// table. This is the single source of truth for how maglevd decides what
// to program into VPP for each backend state. If this test needs updating
// the behavior has deliberately changed.
func TestBackendEffectiveWeight(t *testing.T) {
	cases := []struct {
		name       string
		poolIdx    int
		activePool int
		state      State
		cfgWeight  int
		wantWeight uint8
		wantFlush  bool
	}{
		{"up active w100", 0, 0, StateUp, 100, 100, false},
		{"up active w50", 0, 0, StateUp, 50, 50, false},
		{"up active w0", 0, 0, StateUp, 0, 0, false},
		{"up active clamp-high", 0, 0, StateUp, 150, 100, false},
		{"up active clamp-low", 0, 0, StateUp, -5, 0, false},

		{"up standby pool0 active=1", 0, 1, StateUp, 100, 0, false},
		{"up standby pool1 active=0", 1, 0, StateUp, 100, 0, false},
		{"up standby pool2 active=0", 2, 0, StateUp, 100, 0, false},

		{"up failover pool1 active=1", 1, 1, StateUp, 100, 100, false},

		{"unknown pool0 active=0", 0, 0, StateUnknown, 100, 0, false},
		{"unknown pool1 active=0", 1, 0, StateUnknown, 100, 0, false},

		{"down pool0 active=0", 0, 0, StateDown, 100, 0, false},
		{"down pool1 active=1", 1, 1, StateDown, 100, 0, false},

		{"paused pool0 active=0", 0, 0, StatePaused, 100, 0, false},

		{"disabled pool0 active=0", 0, 0, StateDisabled, 100, 0, true},
		{"disabled pool1 active=1", 1, 1, StateDisabled, 100, 0, true},
	}

	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			w, f := BackendEffectiveWeight(tc.poolIdx, tc.activePool, tc.state, tc.cfgWeight)
			if w != tc.wantWeight {
				t.Errorf("weight: got %d, want %d", w, tc.wantWeight)
			}
			if f != tc.wantFlush {
				t.Errorf("flush: got %v, want %v", f, tc.wantFlush)
			}
		})
	}
}

// TestActivePoolIndex locks down the priority-failover selector: the first
// pool containing at least one up backend is the active pool. Default 0.
func TestActivePoolIndex(t *testing.T) {
	mkFE := func(pools ...[]string) config.Frontend {
		out := make([]config.Pool, len(pools))
		for i, p := range pools {
			out[i] = config.Pool{Name: "p", Backends: map[string]config.PoolBackend{}}
			for _, name := range p {
				out[i].Backends[name] = config.PoolBackend{Weight: 100}
			}
		}
		return config.Frontend{Pools: out}
	}

	cases := []struct {
		name   string
		fe     config.Frontend
		states map[string]State
		want   int
	}{
		{
			name:   "pool0 has up, pool1 standby",
			fe:     mkFE([]string{"a", "b"}, []string{"c", "d"}),
			states: map[string]State{"a": StateUp, "b": StateDown, "c": StateUp, "d": StateUp},
			want:   0,
		},
		{
			name:   "pool0 all down, pool1 has up → failover",
			fe:     mkFE([]string{"a", "b"}, []string{"c", "d"}),
			states: map[string]State{"a": StateDown, "b": StateDown, "c": StateUp, "d": StateUp},
			want:   1,
		},
		{
			name:   "pool0 all disabled, pool1 has up → failover",
			fe:     mkFE([]string{"a", "b"}, []string{"c"}),
			states: map[string]State{"a": StateDisabled, "b": StateDisabled, "c": StateUp},
			want:   1,
		},
		{
			name:   "pool0 all paused, pool1 has up → failover",
			fe:     mkFE([]string{"a"}, []string{"c"}),
			states: map[string]State{"a": StatePaused, "c": StateUp},
			want:   1,
		},
		{
			name:   "pool0 all unknown (startup), pool1 up → pool1",
			fe:     mkFE([]string{"a"}, []string{"c"}),
			states: map[string]State{"a": StateUnknown, "c": StateUp},
			want:   1,
		},
		{
			name:   "nothing up anywhere → default 0",
			fe:     mkFE([]string{"a"}, []string{"c"}),
			states: map[string]State{"a": StateDown, "c": StateDown},
			want:   0,
		},
		{
			name:   "1 up in pool0 is enough",
			fe:     mkFE([]string{"a", "b", "c"}, []string{"d"}),
			states: map[string]State{"a": StateDown, "b": StateDown, "c": StateUp, "d": StateUp},
			want:   0,
		},
		{
			name:   "three tiers, pool0 and pool1 both empty → pool2",
			fe:     mkFE([]string{"a"}, []string{"b"}, []string{"c"}),
			states: map[string]State{"a": StateDown, "b": StateDown, "c": StateUp},
			want:   2,
		},
	}

	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			got := ActivePoolIndex(tc.fe, tc.states)
			if got != tc.want {
				t.Errorf("got pool %d, want pool %d", got, tc.want)
			}
		})
	}
}

// TestComputeFrontendState locks down the reduction rule: frontends are
// up iff any backend has effective weight > 0, unknown iff all backends
// are still in StateUnknown (or there are no backends), and down otherwise.
func TestComputeFrontendState(t *testing.T) {
	mkFE := func(pools ...[]string) config.Frontend {
		out := make([]config.Pool, len(pools))
		for i, p := range pools {
			out[i] = config.Pool{Name: "p", Backends: map[string]config.PoolBackend{}}
			for _, name := range p {
				out[i].Backends[name] = config.PoolBackend{Weight: 100}
			}
		}
		return config.Frontend{Pools: out}
	}

	cases := []struct {
		name   string
		fe     config.Frontend
		states map[string]State
		want   FrontendState
	}{
		{
			name: "no backends → unknown",
			fe:   config.Frontend{Pools: []config.Pool{{Name: "primary", Backends: map[string]config.PoolBackend{}}}},
			want: FrontendStateUnknown,
		},
		{
			name:   "all unknown (startup) → unknown",
			fe:     mkFE([]string{"a", "b"}),
			states: map[string]State{"a": StateUnknown, "b": StateUnknown},
			want:   FrontendStateUnknown,
		},
		{
			name:   "one up in primary → up",
			fe:     mkFE([]string{"a", "b"}),
			states: map[string]State{"a": StateUp, "b": StateDown},
			want:   FrontendStateUp,
		},
		{
			name:   "all down → down",
			fe:     mkFE([]string{"a", "b"}),
			states: map[string]State{"a": StateDown, "b": StateDown},
			want:   FrontendStateDown,
		},
		{
			name:   "all disabled → down",
			fe:     mkFE([]string{"a", "b"}),
			states: map[string]State{"a": StateDisabled, "b": StateDisabled},
			want:   FrontendStateDown,
		},
		{
			name:   "all paused → down",
			fe:     mkFE([]string{"a"}),
			states: map[string]State{"a": StatePaused},
			want:   FrontendStateDown,
		},
		{
			name:   "primary down, secondary up → up (failover)",
			fe:     mkFE([]string{"a"}, []string{"b"}),
			states: map[string]State{"a": StateDown, "b": StateUp},
			want:   FrontendStateUp,
		},
		{
			name:   "primary up, secondary down → up (secondary standby ignored)",
			fe:     mkFE([]string{"a"}, []string{"b"}),
			states: map[string]State{"a": StateUp, "b": StateDown},
			want:   FrontendStateUp,
		},
		{
			name:   "primary unknown, secondary unknown → unknown",
			fe:     mkFE([]string{"a"}, []string{"b"}),
			states: map[string]State{"a": StateUnknown, "b": StateUnknown},
			want:   FrontendStateUnknown,
		},
		{
			name:   "primary down, secondary unknown → down",
			fe:     mkFE([]string{"a"}, []string{"b"}),
			states: map[string]State{"a": StateDown, "b": StateUnknown},
			want:   FrontendStateDown,
		},
	}

	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			got := ComputeFrontendState(tc.fe, tc.states)
			if got != tc.want {
				t.Errorf("got %s, want %s", got, tc.want)
			}
		})
	}
}